Wavelength converting layer patterning for LED arrays

ABSTRACT

A method includes depositing a layer comprising a photoinitiator and a curable material onto a surface and applying a nanoimprint mold on the layer of curable material to form a mesh comprising intersecting walls defining cavities. After applying the nanoimprint mold, the mesh is illuminated with light causing decarboxylation of the photoinitiator to initiate curing of the curable material. After curing the curable material, the nanoimprint mold is removed and a wavelength converting material is deposited in the cavities to form an array of wavelength converting pixels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/096,010 filed Nov. 12, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/226,616 filed Dec. 19, 2018, now U.S. Pat. No.10,879,431, which claims benefit of priority to U.S. provisional patentapplication 62/609,440 filed Dec. 22, 2017 and to European PatentApplication EP18164362.8 filed Mar. 27, 2018. Each of theabove-mentioned applications is incorporated herein by reference in itsentirety.

BACKGROUND

Precision control lighting applications can require the production andmanufacturing of light emitting diode (LED) pixel systems. Manufacturingsuch LED pixel systems can require accurate deposition of material dueto the small size of the pixels and the small lane space between thesystems. The miniaturization of components used for such LED pixelsystems may lead to unintended effects that are not present in largerLED pixel systems.

Semiconductor light-emitting devices including LEDs, resonant cavitylight emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs),and edge emitting lasers are among the most efficient light sourcescurrently available. Materials systems currently of interest in themanufacture of high-brightness light emitting devices capable ofoperation across the visible spectrum include Group III-Vsemiconductors, particularly binary, ternary, and quaternary alloys ofgallium, aluminum, indium, and nitrogen, also referred to as III-nitridematerials. Typically, III-nitride light emitting devices are fabricatedby epitaxially growing a stack of semiconductor layers of differentcompositions and dopant concentrations on a sapphire, silicon carbide,III-nitride, composite, or other suitable substrate by metal-organicchemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), orother epitaxial techniques. The stack often includes one or more n-typelayers doped with, for example, Si, formed over the substrate, one ormore light emitting layers in an active region formed over the n-typelayer or layers, and one or more p-type layers doped with, for example,Mg, formed over the active region. Electrical contacts are formed on then- and p-type regions.

III-nitride devices are often formed as inverted or flip chip devices,where both the n- and p-contacts formed on the same side of thesemiconductor structure, and most of the light is extracted from theside of the semiconductor structure opposite the contacts.

SUMMARY

A method for making a patterned wavelength converting layer includesdepositing a layer comprising a photoinitiator and a curable materialonto a surface and applying a nanoimprint mold on the layer of curablematerial to form a mesh comprising intersecting walls defining cavities.After applying the nanoimprint mold, the mesh is illuminated with lightcausing decarboxylation of the photoinitiator to initiate curing of thecurable material. After curing the curable material, the nanoimprintmold is removed and a wavelength converting material is deposited in thecavities to form an array of wavelength converting pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a top view diagram of a 3×3 pixel matrix;

FIG. 1B is a top view diagram of a 10×10 pixel matrix;

FIG. 1C is a diagram of a 3×3 pixel matrix on a sapphire substrate;

FIG. 1D is a cross-section view diagram of an LED array;

FIG. 1E is a cross-section view diagram of a light emitting devices;

FIG. 1F is a method to generate wavelength converting layer segments;

FIG. 1G is a diagram of a siloxane compound;

FIG. 1H is a diagram of a nanoimprint lithography mold on convertermaterial;

FIG. 1I is a diagram of an intermediate step of the nanoimprintlithography mold on converter material of FIG. 1H;

FIG. 1J is a diagram of a top view of a mesh;

FIG. 1K is a cross section view of the mesh of FIG. 1J;

FIG. 2A is a top view of the electronics board with LED array attachedto the substrate at the LED device attach region in one embodiment;

FIG. 2B is a diagram of one embodiment of a two channel integrated LEDlighting system with electronic components mounted on two surfaces of acircuit board;

FIG. 2C is an example vehicle headlamp system; and

FIG. 3 shows an example illumination system.

DETAILED DESCRIPTION

Examples of different light illumination systems and/or light emittingdiode (“LED”) implementations will be described more fully hereinafterwith reference to the accompanying drawings. These examples are notmutually exclusive, and features found in one example may be combinedwith features found in one or more other examples to achieve additionalimplementations. Accordingly, it will be understood that the examplesshown in the accompanying drawings are provided for illustrativepurposes only and they are not intended to limit the disclosure in anyway. Like numbers refer to like elements throughout.

It will be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms may be used todistinguish one element from another. For example, a first element maybe termed a second element and a second element may be termed a firstelement without departing from the scope of the present invention. Asused herein, the term “and/or” may include any and all combinations ofone or more of the associated listed items.

It will be understood that when an element such as a layer, region, orsubstrate is referred to as being “on” or extending “onto” anotherelement, it may be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there may be no intervening elements present. Itwill also be understood that when an element is referred to as being“connected” or “coupled” to another element, it may be directlyconnected or coupled to the other element and/or connected or coupled tothe other element via one or more intervening elements. In contrast,when an element is referred to as being “directly connected” or“directly coupled” to another element, there are no intervening elementspresent between the element and the other element. It will be understoodthat these terms are intended to encompass different orientations of theelement in addition to any orientation depicted in the figures.

Relative terms such as “below,” “above,” “upper,”, “lower,” “horizontal”or “vertical” may be used herein to describe a relationship of oneelement, layer, or region to another element, layer, or region asillustrated in the figures. It will be understood that these terms areintended to encompass different orientations of the device in additionto the orientation depicted in the figures.

Semiconductor light emitting devices (LEDs) or optical power emittingdevices, such as devices that emit ultraviolet (UV) or infrared (IR)optical power, are among the most efficient light sources currentlyavailable. These devices (hereinafter “LEDs”), may include lightemitting diodes, resonant cavity light emitting diodes, vertical cavitylaser diodes, edge emitting lasers, or the like. Due to their compactsize and lower power requirements, for example, LEDs may be attractivecandidates for many different applications. For example, they may beused as light sources (e.g., flash lights and camera flashes) forhand-held battery-powered devices, such as cameras and cell phones. Theymay also be used, for example, for automotive lighting, heads up display(HUD) lighting, horticultural lighting, street lighting, torch forvideo, general illumination (e.g., home, shop, office and studiolighting, theater/stage lighting and architectural lighting), augmentedreality (AR) lighting, virtual reality (VR) lighting, as back lights fordisplays, and IR spectroscopy. A single LED may provide light that isless bright than an incandescent light source, and, therefore,multi-junction devices or arrays of LEDs (such as monolithic LED arrays,micro LED arrays, etc.) may be used for applications where morebrightness is desired or required.

According to embodiments of the disclosed subject matter, LED arrays(e.g., micro LED arrays) may include an array of pixels as shown inFIGS. 1A, 1B, and/or 1C. LED arrays may be used for any applicationssuch as those requiring precision control of LED array segments. Pixelsin an LED array may be individually addressable, may be addressable ingroups/subsets, or may not be addressable. In FIG. 1A, a top view of aLED array 110 with pixels 111 is shown. An exploded view of a 3×3portion of the LED array 110 is also shown in FIG. 1A. As shown in the3×3 portion exploded view, LED array 110 may include pixels 111 with awidth w₁ of approximately 100 μm or less (e.g., 40 μm). The lanes 113between the pixels may be separated by a width, w₂, of approximately 20μm or less (e.g., 5 μm). The lanes 113 may provide an air gap betweenpixels or may contain other material, as shown in FIGS. 1B and 1C andfurther disclosed herein. The distance d₁ from the center of one pixel111 to the center of an adjacent pixel 111 may be approximately 120 μmor less (e.g., 45 μm). It will be understood that the widths anddistances provided herein are examples only, and that actual widthsand/or dimensions may vary.

It will be understood that although rectangular pixels arranged in asymmetric matrix are shown in FIGS. 1A, B and C, pixels of any shape andarrangement may be applied to the embodiments disclosed herein. Forexample, LED array 110 of FIG. 1A may include, over 10,000 pixels in anyapplicable arrangement such as a 100×100 matrix, a 1200×50 matrix, asymmetric matrix, a non-symmetric matrix, or the like. It will also beunderstood that multiple sets of pixels, matrixes, and/or boards may bearranged in any applicable format to implement the embodiments disclosedherein.

FIG. 1B shows a cross section view of an example LED array 1000. Asshown, the pixels 1010, 1020, and 1030 correspond to three differentpixels within an LED array such that a separation sections 1041 and/orn-type contacts 1040 separate the pixels from each other. According toan embodiment, the space between pixels may be occupied by an air gap.As shown, pixel 1010 includes an epitaxial layer 1011 which may be grownon any applicable substrate such as, for example, a sapphire substrate,which may be removed from the epitaxial layer 1011. A surface of thegrowth layer distal from contact 1015 may be substantially planar or maybe patterned. A p-type region 1012 may be located in proximity to ap-contact 1017. An active region 1021 may be disposed adjacent to then-type region and a p-type region 1012. Alternatively, the active region1021 may be between a semiconductor layer or n-type region and p-typeregion 1012 and may receive a current such that the active region 1021emits light beams. The p-contact 1017 may be in contact with SiO2 layers1013 and 1014 as well as plated metal layer 1016 (e.g., plated copper).The n type contacts 1040 may include an applicable metal such as Cu. Themetal layer 1016 may be in contact with a contact 1015 which may bereflective.

Notably, as shown in FIG. 1B, the n-type contact 1040 may be depositedinto trenches 1130 created between pixels 1010, 1020, and 1030 and mayextend beyond the epitaxial layer. Separation sections 1041 may separateall (as shown) or part of a wavelength converting layer 1050. It will beunderstood that a LED array may be implemented without such separationsections 1041 or the separation sections 1041 may correspond to an airgap. The separation sections 1041 may be an extension of the n-typecontacts 1040, such that, separation sections 1041 are formed from thesame material as the n-type contacts 1040 (e.g., copper). Alternatively,the separation sections 1041 may be formed from a material differentthan the n-type contacts 1040. According to an embodiment, separationsections 1041 may include reflective material. The material inseparation sections 1041 and/or the n-type contact 1040 may be depositedin any applicable manner such as, for example, but applying a meshstructure which includes or allows the deposition of the n-type contact1040 and/or separation sections 1041. Wavelength converting layer 1050may have features/properties similar to wavelength converting layer 205of FIG. 1D. As noted herein, one or more additional layers may coat theseparation sections 1041. Such a layer may be a reflective layer, ascattering layer, an absorptive layer, or any other applicable layer.One or more passivation layers 1019 may fully or partially separate then-contact 1040 from the epitaxial layer 1011.

The epitaxial layer 1011 may be formed from any applicable material toemit photons when excited including sapphire, SiC, GaN, Silicone and maymore specifically be formed from a III-V semiconductors including, butnot limited to, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP,InAs, InSb, II-VI semiconductors including, but not limited to, ZnS,ZnSe, CdSe, CdTe, group IV semiconductors including, but not limited toGe, Si, SiC, and mixtures or alloys thereof. These examplesemiconductors may have indices of refraction ranging from about 2.4 toabout 4.1 at the typical emission wavelengths of LEDs in which they arepresent. For example, III-Nitride semiconductors, such as GaN, may haverefractive indices of about 2.4 at 500 nm, and III-Phosphidesemiconductors, such as InGaP, may have refractive indices of about 3.7at 600 nm. Contacts coupled to the LED device 1200 may be formed from asolder, such as AuSn, AuGa, AuSi or SAC solders.

The n-type region may be grown on a growth substrate and may include oneor more layers of semiconductor material that include differentcompositions and dopant concentrations including, for example,preparation layers, such as buffer or nucleation layers, and/or layersdesigned to facilitate removal of the growth substrate. These layers maybe n-type or not intentionally doped, or may even be p-type devicelayers. The layers may be designed for particular optical, material, orelectrical properties desirable for the light emitting region toefficiently emit light. Similarly, the p-type region 1012 may includemultiple layers of different composition, thickness, and dopantconcentrations, including layers that are not intentionally doped, orn-type layers. An electrical current may be caused to flow through thep-n junction (e.g., via contacts) and the pixels may generate light of afirst wavelength determined at least in part by the bandgap energy ofthe materials. A pixel may directly emit light (e.g., regular or directemission LED) or may emit light into a wavelength converting layer 1050(e.g., phosphor converted LED, “PCLED”, etc.) that acts to furthermodify wavelength of the emitted light to output a light of a secondwavelength.

Although FIG. 1B shows an example LED array 1000 with pixels 1010, 1020,and 1030 in an example arrangement, it will be understood that pixels inan LED array may be provided in any one of a number of arrangements. Forexample, the pixels may be in a flip chip structure, a verticalinjection thin film (VTF) structure, a multi junction structure, a thinfilm flip chip (TFFC), lateral devices, etc. For example, a lateral LEDpixel may be similar to a flip chip LED pixel but may not be flippedupside down for direct connection of the electrodes to a substrate orpackage. A TFFC may also be similar to a flip chip LED pixel but mayhave the growth substrate removed (leaving the thin film semiconductorlayers un-supported). In contrast, the growth substrate or othersubstrate may be included as part of a flip chip LED.

The wavelength converting layer 1050 may be in the path of light emittedby active region 1021, such that the light emitted by active region 1021may traverse through one or more intermediate layers (e.g., a photoniclayer). According to embodiments, wavelength converting layer 1050 ormay not be present in LED array 1000. The wavelength converting layer1050 may include any luminescent material, such as, for example,phosphor particles in a transparent or translucent binder or matrix, ora ceramic phosphor element, which absorbs light of one wavelength andemits light of a different wavelength. The thickness of a wavelengthconverting layer 1050 may be determined based on the material used orapplication/wavelength for which the LED array 1000 or individual pixels1010, 1020, and 1030 is/are arranged. For example, a wavelengthconverting layer 1050 may be approximately 20 μm, 50 μm or 1200 μm. Thewavelength converting layer 1050 may be provided on each individualpixel, as shown, or may be placed over an entire LED array 1000.

Primary optic 1022 may be on or over one or more pixels 1010, 1020,and/or 1030 and may allow light to pass from the active region 101and/or the wavelength converting layer 1050 through the primary optic.Light via the primary optic may generally be emitted based on aLambertian distribution pattern such that the luminous intensity of thelight emitted via the primary optic 1022, when observed from an idealdiffuse radiator, is directly proportional to the cosine of the anglebetween the direction of the incident light and the surface normal. Itwill be understood that one or more properties of the primary optic 1022may be modified to produce a light distribution pattern that isdifferent than the Lambertian distribution pattern.

Secondary optics which include one or both of the lens 1065 andwaveguide 1062 may be provided with pixels 1010, 1020, and/or 1030. Itwill be understood that although secondary optics are discussed inaccordance with the example shown in FIG. 1B with multiple pixels,secondary optics may be provided for single pixels. Secondary optics maybe used to spread the incoming light (diverging optics), or to gatherincoming light into a collimated beam (collimating optics). Thewaveguide 1062 may be coated with a dielectric material, a metallizationlayer, or the like and may be provided to reflect or redirect incidentlight. In alternative embodiments, a lighting system may not include oneor more of the following: the wavelength converting layer 1050, theprimary optics 1022, the waveguide 1062 and the lens 1065.

Lens 1065 may be formed form any applicable transparent material suchas, but not limited to SiC, aluminum oxide, diamond, or the like or acombination thereof. Lens 1065 may be used to modify the a beam of lightto be input into the lens 1065 such that an output beam from the lens1065 will efficiently meet a desired photometric specification.Additionally, lens 1065 may serve one or more aesthetic purpose, such asby determining a lit and/or unlit appearance of the multiple LED devices1200B.

FIG. 1C shows a cross section of a three dimensional view of a LED array1100. As shown, pixels in the LED array 1100 may be separated bytrenches which are filled to form n-contacts 1140. The pixels may begrown on a substrate 1114 and may include a p-contact 1113, a p-GaNsemiconductor layer 1112, an active region 1111, and an n-Gansemiconductor layer 1110. It will be understood that this structure isprovided as an example only and one or more semiconductor or otherapplicable layers may be added, removed, or partially added or removedto implement the disclosure provided herein. A wavelength convertinglayer 1117 may be deposited on the semiconductor layer 1110 (or otherapplicable layer).

Passivation layers 1115 may be formed within the trenches 1130 andn-contacts 1140 (e.g., copper contacts) may be deposited within thetrenches 1130, as shown. The passivation layers 1115 may separate atleast a portion of the n-contacts 1140 from one or more layers of thesemiconductor. According to an implementation, the n-contacts 1140, orother applicable material, within the trenches may extend into thewavelength converting layer 1117 such that the n-contacts 1140, or otherapplicable material, provide complete or partial optical isolationbetween the pixels.

FIG. 1D shows an example pixel array 1200 manufactured in accordancewith the techniques disclosed herein may include light-emitting devices1270 that include a GaN layer 1250, active region 1290, solder 1280, andpattern sapphire substrate (PSS) pattern 1260. Wavelength convertinglayers 1220 may be disposed onto the light emitting devices 1270 inaccordance with the techniques disclosed herein to create pixels 1275.

Optical isolation materials 1230 may be applied to the wavelengthconverting layer 1220. A wavelength converting layer may be mounted ontoa GaN layer 1250 via a pattern sapphire substrate (PSS) pattern 1260.The GaN layer 1250 may be bonded to or grown over an active region 1290and the light-emitting device 1270 may include a solder 1280. Opticalisolator material 1240 may also be applied to the sidewalls of the GaNlayer 1250.

As an example, the pixels 1275 of FIG. 1D may correspond to the pixels111 of FIG. 1 b . When the pixels 111 or 1275 are activated, therespective active regions 1290 of the pixels may generate a light. Thelight may pass through the wavelength converting layer 1220 and maysubstantially be emitted from the surface of the wavelength convertinglayer 1220.

FIG. 1E shows components of the pixel array of FIG. 1D prior to thewavelength converting layer 1220 being placed on the light emittingdevices 1270.

FIG. 1F shows a method 1400 for generating a wavelength converting layerwith a sol-gel or siloxane binder. As shown at step 1410 a wavelengthconverting layer may be deposited onto a surface. The surface may be anyapplicable surface such as a support surface such as a glass supportsurface, a tape such as a stretchable tape, a blue tape, a white tape, aUV tape, or any other surface configured to hold the wavelengthconverting layer. The surface may contain walls to hold the wavelengthconverting layer material.

The wavelength converting layer may include a plurality of opticallyisolating particles such as, but not limited to phosphor grains with orwithout activation from rare earth ions, zinc barium borate, aluminumnitride, aluminum oxynitride (AlON), barium sulfate, barium titanate,calcium titanate, cubic zirconia, diamond, gadolinium gallium garnet(GGG), lead lanthanum zirconate titanate (PLZT), lead zirconate titanate(PZT), sapphire, silicon aluminum oxynitride (SiAlON), silicon carbide,silicon oxynitride (SiON), strontium titanate, titanium oxide, yttriumaluminum garnet (YAG), zinc selenide, zinc sulfide, and zinc telluride,diamond, silicon carbide (SiC), single crystal aluminum nitride (AlN),gallium nitride (GaN), or aluminum gallium nitride (AlGaN) or anytransparent, translucent, or scattering ceramic, optical glass, highindex glass, sapphire, alumina, III-V semiconductors such as galliumphosphide, II-VI semiconductors such as zinc sulfide, zinc selenide, andzinc telluride, group IV semiconductors and compounds, metal oxides,metal fluorides, an oxide of any of the following: aluminum, antimony,arsenic, bismuth, calcium, copper, gallium, germanium, lanthanum, lead,niobium, phosphorus, tellurium, thallium, titanium, tungsten, zinc, orzirconium, polycrystalline aluminum oxide (transparent alumina),aluminum oxynitride (AlON), cubic zirconia (CZ), gadolinium galliumgarnet (GGG), gallium phosphide (GaP), lead zirconate titanate (PZT),silicon aluminum oxynitride (SiAlON), silicon carbide (SiC), siliconoxynitride (SiON), strontium titanate, yttrium aluminum garnet (YAG),zinc sulfide (ZnS), spinel, Schott glass LaFN21, LaSFN35, LaF2, LaF3,LaF10, NZK7, NLAF21, LaSFN18, SF59, or LaSF3, Ohara glass SLAM60 orSLAH51, and may comprise nitride luminescent material, garnetluminescent material, orthosilicate luminescent material, SiAlONluminescent material, aluminate luminescent material, oxynitrideluminescent material, halogenide luminescent material, oxyhalogenideluminescent material, sulfide luminescent material and/or oxysulfideluminescent material, luminescent quantum dots comprising core materialschosen from cadmium sulfide, cadmium selenide, zinc sulfide, zincselenide, and may be chosen form SrLiAl₃N₄:Eu (II)(strontium-lithium-aluminum nitride: europium (II)) class, Eu(II) dopednitride phosphors like (Ba,Sr,Ca)2Si5-xAlxOxN8:Eu, (Sr,Ca)SiAlN3:Eu orSrLiAl3N4:Eu, or any combination thereof.

The wavelength converting layer may include binder material such thatthe binder material is either siloxane material or sol-gel material orhybrid combinations of sol-gel and siloxane, as well as polysilazaneprecursor polymers in combination with siloxanes. Siloxane materialand/or sol-gel material may be as a binder as such material may beconfigured to remain functional under the high flux and temperaturerequirements of LED pixels and pixel arrays.

Siloxane material may be siloxane polymer where siloxane is a functionalgroup in organosilicon chemistry with the Si—O—Si linkage, as shown inFIG. 1G via compound 1500. Parent siloxanes may include oligomeric andpolymeric hydrides with the formulae H(OSiH₂)_(n)OH and (OSiH₂)_(n).Siloxanes may also include branched compounds, the defining feature ofwhich may be that each pair of silicon centres is separated by oneoxygen atom. Siloxane material may adopt structures expected for linkedtetrahedral (“sp³-like”) centers. The Si—O bond may be 1.64 Å (vs Si—Cdistance of 1.92 Å) and the Si—O—Si angle may be open at 142.5°.Siloxanes may have low barriers for rotation about the Si—O bonds as aconsequence of low steric hindrance.

A siloxane binder may be formed via a condensation reaction such thatmolecules join together by losing small molecules as byproducts such aswater or methanol. Alternatively or in addition, a siloxane binder maybe formed via ring-opening polymerization such that the terminal end ofa polymer chain acts as a reactive center where further cyclic monomerscan react by opening its ring system and form a longer polymer chain.The condensation reaction and/or the ring-opening polymerization may beconsidered a form of chain-growth polymerization.

A sol-gel binder may be created via a sol-gel process using awet-chemical technique. In such a process a solution may evolvegradually towards the formation of a gel-like network containing both aliquid and a solid phase. Precursors such as metal alkoxides and metalchlorides, which undergo hydrolysis and polycondensation reactions, maybe used during the sol-gel process. The solution (sol) may containcolloids and a colloidal dispersion may be a solid-liquid and/orliquid/liquid mixture, which contains solid particles, dispersed invarious degrees in a liquid medium. A sol-gel binder may be formed via acondensation reaction such that molecules join together by losing smallmolecules as byproducts such as water or methanol. Precursor polymerssuch as polysilazanes and polysilazane-siloxane hybrid materials mayalso be used as binders. Polysilzanes are precursor polymers containingthe —HN—Si motif which is highly reactive with silanols (Si—OH) andalcohols (C—OH) to form siloxane bonds (Si—O—) with elimination ofammonia (NH3). Polysilazane-based precursor liquids are commerciallyavailable as “Spin-On-Glass” materials. They are typically used to castSiO2 dielectric films.

The binder to bind a wavelength converting layer may need to experiencerapid curing and low volatility in order facilitate a nanoimprintlithography (NIL) process as disclosed herein. Accordingly, thewavelength converting layer may contain a photoinitiator, and thephotoinitiator may be used to catalyze the curing process of the binder.A NIL process may be applied to the wavelength converting layer tosegment the wavelength converting layer into wavelength converting layersegments that can be applied to light emitting devices. As shown in FIG.1F, at step 1420, a NIL mold may be applied to the wavelength convertinglayer. FIG. 1H illustrates a cross-sectional view of a NIL mold 1610being applied to a wavelength converting layer 1620. As shown, the NILmold 1610 may be deposited such that wavelength converting layer 1620changes its form to that of the mold 1610. It should be noted that thespace between the teeth of the mold 1610 may correspond to the spacingrequired to place wavelength converting layer segments onto spaced lightemitting devices.

At step 1430 of FIG. 1F, the wavelength converting layer may be cured.The curing may be conducted using a UV radiation or a combination of UVradiation and a thermal cure. All or portions of the wavelengthconverting layer may be exposed to UV radiation such that those sectionscan be cured. UV light may be emitted onto the wavelength convertinglayer from any applicable direction and may be applied through the NILmold if the mold is fully or partially transparent.

The UV light may produce a rapid curing process via the use of acatalyst to expedite the reactions required to complete the cure. The UVlight may emit onto a photoinitiator contained in the wavelengthconverting layer and the photoinitiator may react with the UV light. Thephotoinitiator may be, for example, a salt created by interactions ofbases with an acid that is capable of undergoing photodecarboxylation.The photoinitiator may be a salt compound created when an acid and abase pair up to form a neutral species.

The photoinitiator may be configured to undergo the photodecarboxylationprocess when UV light is emitted onto the photoinitiator. A compoundcontained in the photoinitiator, such as an organic acid, may react withthe light such that it decomposes by losing carbon dioxide (CO2). Suchdecarboxylation may effectively remove the acid from the photoinitiatorand a byproduct of the decarboxylation may be, for example, a super basealong with other non-acidic residues. The super base may be, forexample, 1,5-diazabicyclo [5.4.0] undec-5-ene (DBU), 1,5,7-triazabicyclo[4.4.0] dec-5-ene (TBD). The super base may have properties such that itseeks other molecules to park excess electrons which may lead tocatalytic action on reactive chain ends or crosslinkable substrates ofthe sol-gel or siloxane binder.

The super base or other non-acidic residues may be removed from thewavelength converting layer by evaporation or further decompositionduring a thermal cure or postbake.

As shown at step 1440 of FIG. 1F, the nanoimprint mold may be removedfrom the wavelength converting layer as the wavelength converting layermay contain wavelength converting layer segments that are shaped duringthe curing process. At step 1450 of FIG. 1F wavelength converting layersegments may be sized and placed such that they can be attached to anarray of light emitting devices such as the array of light emittingdevices 1201 of FIG. 1E to produce the pixel array 1200 of FIG. 1D. Itwill be noted that a separation step may be required to separate thewavelength converting layer to form the wavelength converting layersegments and may include any applicable such as sawing, etching, laseretching, or the like. It will also be noted that the wavelengthconverting layer segments may be attached to light emitting devices viaany applicable transfer method such as by using a transfer tape,transfer substrate, or the like.

FIG. 1I shows an intermediate step of the cross-sectional view of a NILmold 1610 being applied to a wavelength converting layer 1620, of FIG.1I. As shown, the wavelength converting layer 1620 may be partiallyformed such that wavelength converting layer 1620 corresponds to theportion that is cured with, for example, via UV light such that thephotoinitiator experiences decarboxylation. A second wavelengthconverting layer 1630 may be partially formed such that it may beexperiencing decarboxylation. A byproduct of super base 1631 may remainat this intermediate step, as shown.

According to an implementation of the disclosed subject matter, directprinting using ink jet or similar printing machines may be used todeposit a wavelength converting layer onto light emitting devices. Apattern may be generated on a releasable substrate such as a photolithor imprint litho. Atomic layer deposition (ALD) may be used to pattern alayer using, for example, liftoff to remove the undesirable areas.Kateeva or similar printers can be used to print each layer with, forexample, a TiOx layer at the below a phosphor layer. Notably, suchdirect printing may require the phosphor particles to be significantlysmaller than space made available via the nozzles. Accordingly, 1 um orless phosphor particle size may be used for such a deposition.

According to an implementation of the disclosed subject matter, FIG. 1Jshows a top view and FIG. 1K shows a cross-sectional view of a mesh wall1715 that may be generated to provide a structure for a wavelengthconverting layers 1220 of FIG. 1D when manufacturing the pixel array ofFIG. 1D. The mesh wall 1715 may contain cavities 1714 with space thatcorrespond to the space between light emitting devices 1270 of FIG. 1Esuch that the mesh wall is spaced for the cavities 1714 to align withthe light emitting devices 1270 of FIG. 1E prior to the attaching thewavelength converting layers 1220 of FIG. 1D. The mesh walls may beformed using a nanoimprint (NIL) lithography process or a contact printprocess. A NIL process may be used to generate the mesh walls bydepositing a mesh wall material onto a surface and applying ananoimprint mold onto the material. The mesh wall material may be curedusing thermal curing or using UV light and the nanoimprint mold may beremoved from the mesh wall material. The resulting mesh wall may bedeposited onto the pixel array to create supports for the deposition ofa wavelength converting layers 1220 of FIG. 1D. Alternatively, the meshfilm may be generated contact printing photonic columns with, forexample, sacrificial PMMA or with UV curable material.

FIG. 2A is a top view of an electronics board with an LED array 410attached to a substrate at the LED device attach region 318 in oneembodiment. The electronics board together with the LED array 410represents an LED system 400A. Additionally, the power module 312receives a voltage input at Vin 497 and control signals from theconnectivity and control module 316 over traces 418B, and provides drivesignals to the LED array 410 over traces 418A. The LED array 410 isturned on and off via the drive signals from the power module 312. Inthe embodiment shown in FIG. 2A, the connectivity and control module 316receives sensor signals from the sensor module 314 over trace 418C. Thepixels in LED array 410 may be generated in accordance with the stepsoutlined in FIG. 1F and may be based on the techniques disclosed hereinrelated to FIGS. 1G-I.

FIG. 2B illustrates one embodiment of a two channel integrated LEDlighting system with electronic components mounted on two surfaces of acircuit board 499. As shown in FIG. 2B, an LED lighting system 400Bincludes a first surface 445A having inputs to receive dimmer signalsand AC power signals and an AC/DC converter circuit 412 mounted on it.The LED system 400B includes a second surface 445B with the dimmerinterface circuit 415, DC-DC converter circuits 440A and 440B, aconnectivity and control module 416 (a wireless module in this example)having a microcontroller 472, and an LED array 410 mounted on it. TheLED array 410 is driven by two independent channels such as firstchannel 411A and second channel 411B. In alternative embodiments, asingle channel may be used to provide the drive signals to an LED array,or any number of multiple channels may be used to provide the drivesignals to an LED array.

The LED array 410 may include two groups of LED devices. In an exampleembodiment, the LED devices of group A are electrically coupled to afirst channel 411A and the LED devices of group B are electricallycoupled to a second channel 411B. Each of the two DC-DC converters 440Aand 440B may provide a respective drive current via single channels 411Aand 411B, respectively, for driving a respective group of LEDs A and Bin the LED array 410. The LEDs in one of the groups of LEDs may beconfigured to emit light having a different color point than the LEDs inthe second group of LEDs. Control of the composite color point of lightemitted by the LED array 410 may be tuned within a range by controllingthe current and/or duty cycle applied by the individual DC/DC convertercircuits 440A and 440B via a single channel 411A and 411B, respectively.Although the embodiment shown in FIG. 2B does not include a sensormodule (as described in FIG. 2A), an alternative embodiment may includea sensor module.

The illustrated LED lighting system 400B is an integrated system inwhich the LED array 410 and the circuitry for operating the LED array410 are provided on a single electronics board. Connections betweenmodules on the same surface of the circuit board 499 may be electricallycoupled for exchanging, for example, voltages, currents, and controlsignals between modules, by surface or sub-surface interconnections,such as traces 431, 432, 433, 434 and 435 or metallizations (not shown).Connections between modules on opposite surfaces of the circuit board499 may be electrically coupled by through board interconnections, suchas vias and metallizations (not shown). As disclosed herein, the pixelsin LED array 410 may be generated in accordance with the steps outlinedin FIG. 1F and may be based on the techniques disclosed herein relatedto FIGS. 1G-I.

According to embodiments, LED systems may be provided where an LED arrayis on a separate electronics board from the driver and controlcircuitry. According to other embodiments, a LED system may have the LEDarray together with some of the electronics on an electronics boardseparate from the driver circuit. For example, an LED system may includea power conversion module and an LED module located on a separateelectronics board than the LED arrays.

According to embodiments, an LED system may include a multi-channel LEDdriver circuit. For example, an LED module may include embedded LEDcalibration and setting data and, for example, three groups of LEDs. Oneof ordinary skill in the art will recognize that any number of groups ofLEDs may be used consistent with one or more applications. IndividualLEDs within each group may be arranged in series or in parallel and thelight having different color points may be provided. For example, warmwhite light may be provided by a first group of LEDs, a cool white lightmay be provided by a second group of LEDs, and a neutral white light maybe provided by a third group.

FIG. 2C shows an example vehicle headlamp system 300 including a vehiclepower 302 including a data bus 304. A sensor module 307 may be connectedto the data bus 304 to provide data related to environment conditions(e.g. ambient light conditions, temperature, time, rain, fog, etc.),vehicle condition (parked, in-motion, speed, direction),presence/position of other vehicles, pedestrians, objects, or the like.The sensor module 307 may be similar to or the same as the sensor module314 of FIG. 2A. AC/DC Converter 305 may be connected to the vehiclepower 302.

The power module 312 (AC/DC converter) of FIG. 2C may be the same as orsimilar to the AC/DC converter 412 of FIG. 2B and may receive AC powerfrom the vehicle power 302. It may convert the AC power to DC power asdescribed in FIG. 2B for AC-DC converter 412. The vehicle head lampsystem 300 may include an active head lamp 331 which receives one ormore inputs provided by or based on the AC/DC converter 305,connectivity and control module 306, and/or sensor module 307. As anexample, the sensor module 307 may detect the presence of a pedestriansuch that the pedestrian is not well lit, which may reduce thelikelihood that a driver sees the pedestrian. Based on such sensorinput, the connectivity and control module 306 may output data to theactive head lamp 331 using power provided from the AC/DC converter 305such that the output data activates a subset of LEDs in an LED arraycontained within active head lamp 331. The subset of LEDs in the LEDarray, when activated, may emit light in the direction where the sensormodule 307 sensed the presence of the pedestrian. These subset of LEDsmay be deactivated or their light beam direction may otherwise bemodified after the sensor module 207 provides updated data confirmingthat the pedestrian is no longer in a path of the vehicle that includesvehicle head lamp system. The pixels in an LED array in the active headlamp 331 may be generated in accordance with the steps outlined in FIG.1F and may be based on the techniques disclosed herein related to FIGS.1G-I.

FIG. 3 shows an example system 550 which includes an applicationplatform 560, LED systems 552 and 556, and optics 554 and 558. Thepixels in LED systems 552 and 556 may be generated in accordance withthe steps outlined in FIG. 1F and may be based on the techniquesdisclosed herein related to FIGS. 1G-I. The LED System 552 produceslight beams 561 shown between arrows 561 a and 561 b. The LED System 556may produce light beams 562 between arrows 562 a and 562 b. In theembodiment shown in FIG. 3 , the light emitted from LED System 552passes through secondary optics 554, and the light emitted from the LEDSystem 556 passes through secondary optics 558. In alternativeembodiments, the light beams 561 and 562 do not pass through anysecondary optics. The secondary optics may be or may include one or morelight guides. The one or more light guides may be edge lit or may havean interior opening that defines an interior edge of the light guide.LED systems 552 and/or 556 may be inserted in the interior openings ofthe one or more light guides such that they inject light into theinterior edge (interior opening light guide) or exterior edge (edge litlight guide) of the one or more light guides. LEDs in LED systems 552and/or 556 may be arranged around the circumference of a base that ispart of the light guide. According to an implementation, the base may bethermally conductive. According to an implementation, the base may becoupled to a heat-dissipating element that is disposed over the lightguide. The heat-dissipating element may be arranged to receive heatgenerated by the LEDs via the thermally conductive base and dissipatethe received heat. The one or more light guides may allow light emittedby LED systems 552 and 556 to be shaped in a desired manner such as, forexample, with a gradient, a chamfered distribution, a narrowdistribution, a wide distribution, an angular distribution, or the like.

In example embodiments, the system 550 may be a mobile phone of a cameraflash system, indoor residential or commercial lighting, outdoor lightsuch as street lighting, an automobile, a medical device, AR/VR devices,and robotic devices. The LED System 400A shown in FIG. 2A and vehiclehead lamp system 300 shown in FIG. 2C illustrate LED systems 552 and 556in example embodiments.

The application platform 560 may provide power to the LED systems 552and/or 556 via a power bus via line 565 or other applicable input, asdiscussed herein. Further, application platform 560 may provide inputsignals via line 565 for the operation of the LED system 552 and LEDsystem 556, which input may be based on a user input/preference, asensed reading, a pre-programmed or autonomously determined output, orthe like. One or more sensors may be internal or external to the housingof the application platform 560. Alternatively or in addition, as shownin the LED system 400 of FIG. 2A, each LED System 552 and 556 mayinclude its own sensor module, connectivity and control module, powermodule, and/or LED devices.

In embodiments, application platform 560 sensors and/or LED system 552and/or 556 sensors may collect data such as visual data (e.g., LIDARdata, IR data, data collected via a camera, etc.), audio data, distancebased data, movement data, environmental data, or the like or acombination thereof. The data may be related a physical item or entitysuch as an object, an individual, a vehicle, etc. For example, sensingequipment may collect object proximity data for an ADAS/AV basedapplication, which may prioritize the detection and subsequent actionbased on the detection of a physical item or entity. The data may becollected based on emitting an optical signal by, for example, LEDsystem 552 and/or 556, such as an IR signal and collecting data based onthe emitted optical signal. The data may be collected by a differentcomponent than the component that emits the optical signal for the datacollection. Continuing the example, sensing equipment may be located onan automobile and may emit a beam using a vertical-cavitysurface-emitting laser (VCSEL). The one or more sensors may sense aresponse to the emitted beam or any other applicable input.

In example embodiment, application platform 560 may represent anautomobile and LED system 552 and LED system 556 may representautomobile headlights. In various embodiments, the system 550 mayrepresent an automobile with steerable light beams where LEDs may beselectively activated to provide steerable light. For example, an arrayof LEDs may be used to define or project a shape or pattern orilluminate only selected sections of a roadway. In an exampleembodiment, Infrared cameras or detector pixels within LED systems 552and/or 556 may be sensors (e.g., similar to sensors module 314 of FIG.2A and 307 of FIG. 2C) that identify portions of a scene (roadway,pedestrian crossing, etc.) that require illumination.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs).

The invention claimed is:
 1. A method comprising: forming a mesh havingintersecting walls defining cavities, the mesh comprising aphotoinitiator and a curable material; after forming the mesh,illuminating the mesh with light causing decarboxylation of thephotoinitiator to initiate curing of the curable material; and aftercuring the curable material, depositing a wavelength converting materialin the cavities to form an array of wavelength converting pixels.
 2. Themethod of claim 1, wherein the pixels in the array have widths of 100microns or less and adjacent pixels are spaced apart by 20 microns orless.
 3. The method of claim 1, comprising aligning an array of lightemitting semiconductor diodes with the array of wavelength convertingpixels and attaching each wavelength converting pixel to a correspondinglight emitting semiconductor diode.
 4. The method of claim 1, whereinthe curable material comprises one or more of a siloxane material, apolysilazane, or a sol-gel material.
 5. The method of claim 1, whereinthe photoinitiator is a salt.
 6. The method of claim 1, wherein thedecarboxylated photoinitiator catalyzes reaction of chain ends orcross-linkable substrates of the curable material.
 7. The method ofclaim 1, wherein the decarboxylated photoinitiator catalyzes acondensation polymerization or a ring opening polymerization of thecurable material.
 8. The method of claim 1, wherein the decarboxylationproduces a super base.
 9. The method of claim 8, comprising removing thesuper base by evaporation or thermal decomposition of the super baseafter curing of the curable material.
 10. The method of claim 1,wherein: the curable material comprises one or more of a siloxanematerial, a polysilazane, or a sol-gel material; the photoinitiator is asalt; illuminating the mesh with light comprises illuminating the meshwith ultraviolet light absorbed by the photoinitiator to cause thedecarboxylation of the photoinitiator; and decarboxylation of thephotoinitiator produces a super base.
 11. A wavelength convertingstructure comprising: a mesh having intersecting walls, the meshcomprising a decarboxylated photoinitiator and a cured binder; and aplurality of wavelength converting layers in contact with the mesh wallsforming an array of wavelength converting pixels.
 12. The wavelengthconverting structure of claim 11, wherein the pixels in the array havewidths of 100 microns or less and adjacent pixels are spaced apart by 20microns or less.
 13. A light emitting device comprising: the wavelengthconverting structure of claim 11; and an array of light emittingsemiconductor diodes where each wavelength converting pixels of thewavelength converting structure is attached to a corresponding lightemitting semiconductor diode.
 14. The wavelength converting structure ofclaim 11, wherein the cured binder comprises one or more of a curedsiloxane material, a cured polysilazane, or a cured sol-gel material.15. The wavelength converting structure of claim 11, wherein thedecarboxylated photoinitiator comprises a super base.
 16. A wavelengthconverting structure comprising: a plurality of wavelength convertingelements forming an array of wavelength converting pixels, eachwavelength converting element comprising a decarboxylated photoinitiatorand a cured binder.
 17. The wavelength converting structure of claim 16,wherein the pixels in the array have widths of 100 microns or less andadjacent pixels are spaced apart by 20 microns or less.
 18. A lightemitting device comprising: the wavelength converting structure of claim16; and an array of light emitting semiconductor diodes where eachwavelength converting pixels of the wavelength converting structure isattached to a corresponding light emitting semiconductor diode.
 19. Thewavelength converting structure of claim 16, wherein the cured bindercomprises one or more of a cured siloxane material, a curedpolysilazane, or a cured sol-gel material.
 20. The wavelength convertingstructure of claim 16, wherein the decarboxylated photoinitiatorcomprises a super base.